The Collaborative International Dictionary of English v.0.48:

Impel \Im*pel"\, v. t. [imp. & p. p. Impelled; p. pr. & vb. n.
   Impelling.] [L. impellere; pref. im- in + pellere, pulsum,
   to drive. See Pulse a beat, and cf. Impulse.]
   To drive or urge forward or on; to press on; to incite to
   action or motion in any way.
   [1913 Webster]

         The surge impelled me on a craggy coast. --Pope.

   Syn: To instigate; incite; induce; influence; force; drive;
        urge; actuate; move.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

impelled \impelled\ adj.
   motivated by an irresistable compulsion.

   Syn: driven.
        [WordNet 1.5 +PJC]

WordNet (r) 3.0 (2006):

impelled
    adj 1: urged or forced to action through moral pressure; "felt
           impelled to take a stand against the issue" [syn:
           driven, impelled]